What Firefox add-ons do you use that are useful for programmers?
Firefox addons:
FireBug:helps web developers and designers test and inspect front-end code. It provides us with many useful features such as a console panel for logging information, a DOM inspector, detailed information about page elements, and much, much more.
Web Developer-gives you the power disable CSS, edit CSS on the fly, measure certain areas of a page and much more.
ColorZilla Just click on the icon, hover over the area you'd like to know the hex color for, and click.
Window Resizer to make sure the layout is displayed properly in the standard resolutions of today.
Total Validator validating websites much easier by checking HTML, links, CSS and doing a lot more.